Portable calculator



wosuo KOJIMA 3,493,171

PORTABLE CALCULATOR "Feb. 3

'- 2 Sheets-Sheet 1 Filed March 25, 1968 .F'IG.4

INVENTOR 4 I l l 2 3 4 5 7 DWDDDDDND 9\ Feb. 3, 1970 NOBUO KOJIMAPORTABLE CALCULATOR 2 Sheets-Sheet 2 Filed March 25.. 1968 F l: 6.5 (b

F leQsm) F l G. 5(c) INVENTOR. KOJIMA NOBUO United States Patent O3,493,171 PORTABLE CALCULATOR Nobuo Kojima, Tokyo, Japan, assignor toSama & Etani, Inc., Groton, Mass., a corporation of Massachusetts FiledMar. 25, 1968, Ser. No. 715,626 Claims priority, application Japan, Apr.15, 1967, 42/ 31,608 Int. Cl. G06c 27/00 US. Cl. 235-69 9 ClaimsABSTRACT OF THE DISCLOSURE A portable hand operated calculator having aplurality of elongated strips slidably mounted in a body forlongitudinal movement, each of the strips being formed with a series ofnotches in both sides thereof to receive a stylus tip for calculatingoperations. Projections are provided on the back of the body of thecalculator for engaging the notches by spring means to thereby preventaccidental slippage of the strips when the calculator is handled.

FIELD OF THE INVENTION This invention relates in general to portablecalculators and more particularly concerns a hand operated calculatorhaving a plurality of notched strips and means for engaging the notchesby spring action to prevent slippage of the strips during handling ofthe calculator.

DISCUSSION OF THE PRIOR ART Portable hand operated calculators havingelongated notched strips adapted to be operated by a stylus are wellknown and have been used commercially for a considerable length of time.However, these calculators have been subject to certain deficiencies,one of which is that the setting on the calculator during a computationmay be accidentally disturbed if the calculator should be jarred ordropped. If this occurred in the middle of a series of computations, itwould necessitate starting the entire computation over again. Thisundesirable situation has not been adequately rectified by the prior artcalculators. Some attempts have been made to correct the problem, butthese have either been prohibitively expensive for such a simple machineor have been ineffectual after prolonged use of the calculators.

SUMMARY OF THE INVENTION Broadly speaking, this invention resides in acalculator body having a substantially rigid back and a flexibleindicating front face. A plurality of flexible notched calculatingstrips are slidably mounted within channels in the body and are operableby means of a stylus, the point of which extends through slots in thefront face to engage the notches. Numerical indicia are provided on thefront face and on the calculating strips in such a way as to be viewablethrough windows in the front face. The body is provided with projectionsextending from the back into each channel in which the calculatingstrips slide, these projections being so positioned as to engage thenotches in the strips. As a calculating strip slides in its channel, thetabs between the notches, by which the notches are defined, are allowed,because of the flexibility of both the strip and the front, to pass overthe projections. The back of the body, which is substantially rigid,provides a sur- 3,493,171 Patented Feb. 3, 1970 ice face against whichthe front face acts as a spring to force the projections into engagementwith the notches whenever they are in mutual registration. An L-shapedmember is also slidably mounted in the body and is adapted to abut oneend of all of the strips for clearing the calculator. In this context,clearing means to place all the calculating strips in a zero position sothat the calculator is in condition to commence a new computation.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTReferring now to the drawing and more particularly to FIGS. 1 and 2thereof, there is shown a calculator 11 constructed in accordance withthe principles of this invention having a body 12 comprising asubstantially rigid back 13 and a flexible indicating front face 14. Aplurality of calculating strips 15, 15, 15", etc. are mounted inchannels 16 formed in body 12 so that they may slide longitudinally. Forpurposes of illustration, only a few of calculating strips 15 are shownin FIG. 2. The calculator may include any desired number of calculatingstrips depending upon the number of digits which the calculator isintended to handle. A column of notches 17, 17, 17 etc. is provided oneach vertical edge of each calculating strip. These notches areregularly spaced, sharply defined indentations in the edges of thecalculating strips.

For addition purposes, the digits 0 through 9 are imprinted on the frontside of each strip 15 from near the center toward the top, as shown inFIG. 2. The digits 0 through 9 are imprinted from near the center towardthe bottom of each strip for subtraction purposes. These digits arepositioned in juxtaposition with notches on each of the calculatingstrips. It will be observed that the subtraction digits on calculationstrip 15, which strip corresponds to the least significant digit of thecalculator, are stepped upward one position above the digits of theother strips. It is further evident from the shading shown in FIG. 2that the upper ten notches on the left edge of each strip are surroundedby colored tabs 21. These tabs are between and serve to define notches17. The function of these notches which are thus distinguishable fromthe other notches on the strips will be discussed in detail below.

An L-shaped element 22, which is herein termed a clearing bar, is alsoslidably mounted in body 12 and provides means for clearing thecalculator. Clearing bar 22 also moves toward the top and bottom of thecalculator parallel to the motion of the calculating strips. Clearingbar 22 is shown in its upper or clearing position in FIG. 2. When it isdesired to clear the calculator, the point of stylus 24 (shown in FIG.3) is inserted in hole 25 in clearing bar 22, and the clearing bar ismoved vertically toward the top of calculator 11. as shown in FIG. 1.

The horizontal portion 23 of clearing bar 22 contacts the lower ends ofcalculating strips 15 and moves them all in the same direction so thatthey are all equally positioned, thereby clearing the calculator.

Body 12 is formed with a plurality of walls 26 which project from back13 of body 12 a suflicient distance to substantially meet the undersideof front face 14. These walls 26 form channels 16 therebetween forretaining calculating strips 15 for sliding motion in body 12. Back 13is provided with small projections 27 which extend toward front face 14.These projections have generally rounded surfaces which permit tabs 21to smoothly ride over them, and are shown in the drawing as generallyhemispherical. Projections 27 are substantially shorter than thedistance between back 13 and front face 14. Projections 27 arepositioned in channels 16 so as to engage notches 17. Front face 14 ofbody 12 is sufficiently flexible so that projections 27 engage notches17 by spring action.

As shown in FIG. 1, front face 14 is provided with slots 31, 31', 31",etc. which, when face 14 is properly positioned on back 13, are alignedover the column of notches on the left side of each of calculatingstrips 15 as viewed in FIGS. 1 and 2. At the top of respective slots 31are loops 32, 32, 32", etc. through which appear the notches on theright side of the calculating strips. The function of loops 32 will bedescribed below.

Front face 14 is also provided with windows 33, 33', 33", etc. aboverespective slots 31, which display answers to addition calculations, andwith windows 34, 34', 34", etc. below respective slots 31, which displayanswers to subtraction calculations. Beside each slot 31, front face 14is imprinted with a column 35 of the digits through 9 starting with 0near the bottom of each slot. These digits 35 correspond in size andspacing to the digits imprinted on calculating strips and provideindices for notches 17. The digits which are imprinted on the stripsthemselves only appear in respective windows 33 and 34.

A slot 36 through one side of front face 14 provides access to clearingbar 22 for purposes of clearing the calculator. Hole in clearing bar 22is visible through slot 36. When it is desired to clear the calculator,the point of stylus 24 is inserted through slot 36 into hole 25 andclearing bar 22 is moved vertically toward the top of the calculator tothe position of FIGS. 1 and 2. As shown in these figures, the calculatoris in the cleared or Zero position with Us appearing in all of theaddition windows 33, and 9s appearing in all of the subtraction windows34, except that an arrow pointing toward the bottom of the calculatorappears in the right-hand window 34 corresponding to the leastsignificant digit. In this position the upper colored notches on strips15 do not correspond to any of the digits 0 through 9 imprinted on frontface 14.

When calculator 11 is properly assembled, walls 26, calculating strips15 and clearing bar 22 are each of substantially the same thickness asthe space between front face 14 and back 13. Thus, calculating strips 15are confined by back 13, front face 14 and walls 26 for longitudinalmotion within channels 16. With projections 27 in position in channels16 to register with at least one notch in each of strips 15, thecalculator remains firmly set with whatever setting has beenintentionally entered. However, since front face 14 and strips 15 areflexible, strips 15 are readily movable longitudinally by inserting thepoint of stylus 24 through slots 31 into notches 17 and exerting forceeither toward the top or toward the bottom of the calculator. As eachtab 21 between the notches 17 contacts a projection 27, flexible frontface 14 and strip 15 deform sufficiently to allow that tab to ride overthe projection. While one calculating strip 15 is being moved, theprojections 27 in the unaffected channels maintain engagement withnotches in the remaining strips so that the positions of these stripsare undisturbed.

Some previous calculators have attempted to solve the setting stabilityproblem, to which this invention is directed, by cutting tabs in theback portion of the body and bending them toward the calculating stripsto provide a leaf-spring effect. The useful life of these springs isextremely short when the back is made of thin sheet material. To makesuch a device practical, a substantially heavier back plate wasnecessary with commensurate increases in material, tooling andfabricating costs. Even then there was a substantial amount of mutualwear on the individual leaf springs and the calculating strips and thespring action tended to decrease over a period of time due to thecontinued bending pressures exerted on the leaves with movement of thecalculating strips.

In contrast, the material of the back of body 12 of the calculatorherein described may be made of a relatively thin material such as sheetaluminum. The sheet material is stamped in such a way that smoothlyrounded projections 27 result. This configuration allows tabs 21 betweennotches 17 to ride smoothly over projections 27 while the entire frontface 14 provides the necessary spring action. Thus the spring action ofthe calculator cannot deteriorate and wear on the projections and thecalculating strips is negligible over reasonable operating periods. Theback may also be made of a plastic material with projections 27 moldedthereon. Other materials and methods of making projections 27 could alsobe used.

It is important to note that the specfic configuration of front face 14including the size and position of slots 31 therein, together with theplacement of projections 27 in relation to the slots, as shown in thedrawing, comprises a combination of elements and features particularlyadapted for the intended mechanical action of the calculator. Withreference to FIGS. 1 and 2, it may be observed that two projections 27are positioned in each channel just beyond the end of each elongatedopening (slot 31 and loop 32) in the front face. The projections areseparated by an integral multiple of notch spaces so that both of themsimultaneously register with a notch 17 or a tab 21. When the tabs 21 ofa calculating strip pass over projections 27, the entire oentral portionof the strip tends to bow upward, forcing the adjacent portion of frontface 14 to flex outward against the normal biasing action of the frontface. The decrease in stiffness of the central portion of the front facewhich results from the removal of the material defining the slots allowsstrips 15 to flex easily as they pass over projections 27. However,since the portion of each strip extending between the respectiveprojections 27 is biased toward back '13 by the front face material(unnumbered) between slots 31, the front face portion adjacent a movingstrip is allowed to flex relatively independently of the rest of thefront face. The remainder of the front face thus preserves its biasingpressure on the remaining strips so that they maintain their positionswithin the calculator.

FIGS. 5(a), 5(b) and 5(0) show the steps involved in making computationsby means of this calculator. The direction of movement of the stylusafter insertion into the proper notches is shown by means of arrowsassomated with each of the digits of the numbers used in thecomputations illustrated in the figures. For example, the steps involvedin the addition of the number 576 and 192 will be described withreference to FIGS. 5(a) and 5(b). Stylus 24 is first inserted throughslot 31" into the notch adjacent to the digit 5 on front face 14 andmoves calculating strip 15" toward the bottom of the calculator to thelower limit of that slot. At this point the digit 5 will appear inwindow 33". Similarly, calculatrng strips 15 and 15 are moved in thesame direction so that the figures 7 and 6 appear in windows 33 and 33,respectively. At this time the calculator will have the appearance shownin FIG. 5(a) with colored notches appearing as indicated by the shading.

Whenever a digit to be entered in the calculator is in juxtapositionwith a colored notch, the stylus point engages that notch on thecorresponding strip and moves vertically toward the top of slot 31 withthe strip until the stylus is disengaged by following the curvature ofloop 32 which is smoothly connected to slot 31. As the stylus followsthe curvature of loop 32, the disengaged strip ceases moving and thestylus then engages a notch on the right side of the next strip to theleft. The shape of the loop 32 permits the stylus to move that stripvertically toward the bottom of the calculator the distance of onenotch, in effect carrying the 1 to the next higher significant figure.The stylus is then removed and used to start the next calculation step.

FIG. 5 (b) indicates the steps involved in adding the number 192 to thenumber 576 already registered in the calculator. Since the notchcorresponding to the digit 1 is not colored, it is moved downward in amanner similar to that previously described. However, the notchcorresponding to the digit 9 in slot 31' is colored and the arrowcorresponding to the digit 9 above window 33 shows the movement of thestylus. Stylus 24 is inserted through slot 31' into the notch adjacentdigit 9 and strip is moved as shown by the arrow until the stylusdisengages by following the curvature of loop 32'. At this point strip15 has moved vertically toward the top of the calculator a distancecorresponding to the space between two digits on front face 14, or onenotch width. Strip 15" is subsequently engaged by stylus 24 as itcontinues around loop 32' and is moved vertically toward the bottom ofthe calculator one notch width, thus raising the value of the digitappearing in window 33" by one. The final digit 2 is entered in a mannersimilar to the first digit 1 since it is uncolored as shown in FIG.5(a), and the answer 768 appears in respective addition windows 33.Another set of numbers which may be termed complementary to those in theaddition answer windows appear in the respective subtraction windows 34.The term complementary in this sense means that the numbers in thesubtraction and addition windows, if added, will be a multiple of 10. Inthis instance, since three windows are involved, the sum of the figuresin these two sets of windows should be 1000. The respective numbers are768 and 232, which do indeed add up to 1000;

A subtraction example is illustrated in conjunction with FIGS. 5(b) and5(a) wherein the number 151 will be subtracted from the number 232. Thecalculation starts with the number 232 already appearing in subtractionwindows 34 in FIG. 5(b) resulting from the previous example. The initialcondition of calculator 11 is shown in FIG. 5(1)), while the answer andthe movements of the stylus are shown in FIG. 5(c). Stylus 24 is placedin the uncolored notch as shown in FIG. 5 (b) corresponding to the digit1 in slot 31 and calculating strip 15 is moved vertically toward thebottom of the calculator to the limit of slot 31". The notchcorresponding to the digit 5 in slot 31' is colored and therefore mustbe moved up and around loop 32' as previously described so that stylus24 engages one notch on the right side of calculating strip 15" andmoves that strip vertically toward the bottom of the calculator oneposition. The final digit 1 is then entered in the manner just describedfor the first digit 1. The answer 81 appears in subtraction windows 34,and the complementary figure 919 appears in the addition windows 33.Thus it can be seen that the manipulations required for subtraction areidentical with those required for addition with the exception that thedigits significant to the subtraction operation appear in the lowerwindows 34.

From the above description it is readily apparent that the calculatingstrips move in incremental distances during computations. Theincremental length is the distance between two digits on front face 14which is the same as the distance between two digits on the stripsthemselves. Furthermore, this incremental distance is also equal to thespace between two notches. Whenever the stylus moves a strip toward thetop of the calculator one or more increments because it is inserted intoa colored notch, it

continues on to move the next higher strip toward the bottom of thecalculator one increment only. Each time a computation is completed,stylus 24 is inserted through slot 36 into hole 25 and clearing bar 22is moved toward the top of the calculator until Os appear in all of theaddition answer windows 33.

Having described one embodiment of this invention, it is now apparentthat numerous and varied other embodiments may be devised in accordancewith the principles disclosed herein by those skilled in the art withoutdeparting from the spirit and scope of the invention. Accordingly, theinvention is not to be limited by What has been particularly shown anddescribed, except as indicated in the appended claims.

What is claimed is:

1. A portable calculator comprising:

a body having a back and a flexible indicating front face, said backhaving a plurality of projections extending toward said front face, saidfront face having a plurality of openings therethrough;

a plurality of parallel walls extending from said back toward said frontface, said walls defining therebetween a plurality of channels withinsaid body; and

a plurality of flexible calculating strips each slidably mounted withina respective channel, said strips having a multiplicity of regularlyspaced notches along both edges thereof and also having printed indiciaregularly space on one side thereof, said notches being accessible viacertain of said openings in said front face by which said strips can bemoved distances which are integral multiples of said spaces, thereby toperform computations;

each of said channels having at least one of said projections locatedtherein, said projections being adapted and positioned to engage saidnotches by means of spring action of said flexible front face thereby tobias each of said calculating strips in corresponding channels such thatintentional movement of a selected calculating strip during computationsdoes not cause spurious movement of other calculating strips in theirrespective channels.

2. The portable calculator recited in claim 1, wherein:

said back is made of relatively thin sheet material; and

wherein said sheet material is stamped to form said projections,

each having a smoothly rounded configuration.

3. The portable calculator recited in claim 1, wherein:

said back is made of plastic with said projections molded thereon, saidprojections having a smoothly rounded configuration.

4. The portable calculator recited in claim 1, and further comprising:

a clearing bar slidably mounted within said body and accessible throughone of said openings in said front face, said clearing bar being shapedand configured to clear said calculator by aligning all of saidcalculating strips in a zero position by movement in a single direction.

5. The portable calculator recited in claim 4, wherein:

said calculating strips are biased against said back by said flexiblefront face.

6. The portable calculator recited in claim 5, wherein:

said openings through which said notches are accessible are so shapedand configured to govern the movement of said calculating strips duringcomputations.

7. The portable calculator recited in claim 6, wherein:

said projections extend from said back substantially less than thedistance between said front face and said back, said projections beinggenerally of a smoothly rounded configuration.

8. The portable calculator recited in claim 7, wherein:

said printed indicia on said calculating strips comprise numericaldigits, individual ones of which are visible through openings in saidfront face, one group of digits being visible through one set ofopenings for addition answers and a second group of digits being visiblethrough a second set of openings for subtraction answers.

9. The portable calculator recited in claim 8, wherein:

said front face has printed indicia regularly spaced adjacent saidopenings through which access is made to said notches, said indiciadenoting the numerical positions of said notches.

8 References Cited UNITED STATES PATENTS 1,426,484 8/1922 Krems 235691,661,277 3/1928 Thomas 235-69 2,983,447 5/1961 BuloW 23569 2,988,2736/1961 Feddick 23569 STEPHEN J. TOMSKY, Primary Examiner

